JPH02206961A - Ring back tone transmission circuit - Google Patents

Abstract

PURPOSE:To make an output level of a ring back tone constant at all times by providing a PCM code generator generating a PCM code being the result of PCM-encoding the ring back tone in each ring back tone transmission circuit, and generating the PCM code with a prescribed level for each channel. CONSTITUTION:A digital switch 5 is through to the position of a PCM code generator 4 in the case of transmitting a ring back tone. The PCM code generator 4 generates a PCM code being the result of PCM-encoding the analog ring back tone repetitively and the PCM code is sent to an opposite station from an output terminal 6 through the digital switch 5. The PCM code representing the ring back tone is inputted to an input terminal 7 of the opposite station, a decoder 8 decodes the code into the analog ring back tone with a prescribed level and outputted to a subscriber terminal 1 through a 2/4-wire conversion circuit 2 and sent to a subscriber of the opposite station. Thus, a ring back tone transmission circuit whose transmission level is not fluctuated is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ringback transmission circuit used in a PCM transport device that connects telephone sets through a direct line.

[Conventional technology]

A system shown in FIG. 3 is generally known when connecting telephone sets via a direct line using a PCM transport device. Referring to FIG. 3, when the handset of the first telephone 17 is lifted (off-hook), the off-hook is
The CM terminal device 18 detects the off-hook information and transfers the off-hook information to the second PCM terminal device 19. When the second PCM terminal equipment receives the above-mentioned off-hook information, it sends a paging signal from the ring generator 24 to the second telephone set.

At the same time, a ringback tone is generated from the second PCM terminal device 19 by the ringback tone generator 23 to the first PC.
It is sent to the first telephone 17 through the M terminal equipment 8.

When the handset of the second silver telephone is lifted, the first telephone 17 and the second silver telephone can communicate with each other. Similarly, the first telephone 17 can be called from the second telephone.

Here, a conventional ringback tone sending circuit is shown in FIG.

Referring to FIG. 2, the ringback tone sending circuit is
It is provided in the M terminal equipment.

The ringback tone sending circuit is a switch 10° 2 wire/4
Line (2W/4W) conversion circuit 11. It includes an encoder 12° and a decoder 15. The switch 10 is a subscriber line input terminal a
and is connected to an analog ringback tone generator 16. Also, the encoder 12 is PCM
Connected to output terminal 13.

Decoder 15 is connected to PCM input terminal 14.

When it becomes necessary to send out a ringback tone, the telephone line board 9 operates a switch 10 to connect the output of the ringback tone generator 16 to the 2W/4W conversion circuit 11. When the ringback tone generator 16 is connected to the 2W/4W conversion circuit 1].

A ringback tone is sent from the PCM output terminal 13 to the opposite station via the 2W/4W conversion circuit 11 and the encoder 12.

On the other hand, if you receive a ringback tone.

A 2W/4W conversion circuit 11 is connected to a subscriber line input terminal 9 by a switch 10 and receives a ringback tone via a PCM input terminal 14 and a decoder 15.

This ringback tone is applied to the subscriber line input terminal 9.

[Problem that the invention seeks to solve]

In the conventional ringback tone sending circuit described above, when multiple call bases are activated at the same time.

All of them are connected in parallel to a ringback tone sending circuit. As a result, impedance matching with the subscriber line input terminal of the 2W/4W conversion circuit cannot be achieved, and the sending level of the ringback tone decreases. In other words, there is a problem in that the output level varies depending on the number of communication bases activated at the same time.

Furthermore, considering the case where all communication bases housed in the PCM transport device are activated at the same time, a ringback tone generator with a large output capacity is required. Such ringback tone generators are expensive and require a large installation space.

An object of the present invention is to provide a ringback tone sending circuit in which the sending level does not fluctuate.

Another object of the present invention is to provide a ringback tone sending circuit that does not require an expensive ringback tone and requires less installation space.

[Means for solving problems]

According to the present invention, a transmitted analog signal from a two-wire subscriber line is converted into a PCM code and sent as a transmitted PCM code to a digital line, while a received PCM code from the digital line is converted into an analog signal and a received analog signal is converted into a received analog signal. a PCM code generator that is used in a PCM carrier to provide a signal to the two-wire subscriber line and sends out a ringback tone PCM code; and a PCM code generator that selectively transmits the transmitted PCM code and the tone PCM code to the digital line. A ringback tone transmission circuit is obtained, which is characterized by having a transmission switching means for transmitting a ringback tone.

〔Example〕

Next, the present invention will be explained with reference to examples.

Referring to FIG. 1, 1 is a subscriber terminal connected to a subscriber line, and 2 is a 2 W/4 terminal that converts an audio signal to 2 W/4 W.
W conversion circuit, 3 is an encoder that converts the audio signal into a PCM code, 4 is a PCM code that PCM encodes the ringback tone.
A PCM code generator generates a code, and 5 is a digital switch that switches between the output of the encoder 3 and the output of the PCM code generator 4.

6 Output terminal that sends the IiPCM code to the opposite station.

7 is an input terminal for inputting the PCM code from the opposite station; 8
is a decoder that decodes the PCM code into an analog signal.

In a normal case (in the case of a call), an audio signal input from the terminal 1 is input to the 2W/4W conversion circuit 2 and the complete encoder 3, where it is encoded into a PCM code. This PCM code is sent through the digital switch 5 from the output terminal 6 to the opposite station.

On the other hand, the PCM code input from the opposite station via the input terminal 7 is converted into an analog signal by the decoder 8, and the 2W/4W
The signal is output through the conversion circuit 2 to the subscriber terminal.

When it becomes necessary to send out a ringback tone, the digital switch is switched to the PCM code generator 4 side. PC
The M code generator 4 repeatedly generates a PCM code obtained by PCM encoding an analog ringback tone.
This PCM code is sent through the digital switch 5 from the output terminal 6 to the opposing station. At the opposite station, a PCM code indicating a ringback tone is inputted to an input terminal 7, decoded by a decoder 8 into an analog ringback tone of a predetermined level, and outputted to the subscriber terminal 1 through a 2W/4W conversion circuit 2. . The call is then sent to the subscriber at the opposite station, allowing the subscriber to confirm that the other party is being called.

〔Effect of the invention〕

As explained above, in the present invention, each ringback tone sending circuit is provided with a PCM code generator that generates a PCM code by PCM encoding a ringback tone, Can be configured to generate a code.

Therefore, the output level of the ringback tone to be sent out is always constant, and as a result, the level does not vary depending on the number of communication channels operating simultaneously as in the conventional case.

In addition, the digital switch and PCM code generator can be easily configured with digital circuits, and if IC technology is applied,
It is possible to easily realize a device that is inexpensive, compact, and consumes low power.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of a ringback tone sending circuit according to the present invention, FIG. 2 is a diagram showing a conventional ringback tone sending circuit, and FIG. 3 is a diagram showing a communication line system using a PCM transport device. It is a diagram. ], 9...Subscriber line input terminal, 2.11...2
W/4W conversion circuit, 3.12... Encoder, 4... Digital switch, 5.13... PCM output terminal, 6.
14...PCM input terminal, 7.15...Decoder, 8
...Ringback tone PCM code generator, 1
0...Switching device, 16...Analog type ringback tone generator, 17.20...Subscriber's telephone, 18
．． 19...PCM transport device. 21, 24...RING signal generator, 22.23
...Analog type ringback tone generator. Figure 3

Claims (1)

[Claims] The transmitted analog signal from the 1- and 2-wire subscriber line is converted into a PCM code and sent to the digital line as the transmitted PCM code, while the received PCM code from the digital line is converted to an analog signal and the received analog signal is transmitted as the received analog signal. Used in PCM transport equipment for wire subscriber lines,
A ringback comprising: a PCM code generator that transmits a ringback tone as a tone PCM code; and a transmission switching means that selectively transmits the transmission PCM code and the tone PCM code to the digital line. Tone sending circuit.